Conventionally, as an overcurrent protection apparatus that protects a circuit from an overcurrent, a fuse is known (see JP 9-17323A).
The fuse is connected in series to a circuit that is to be protected. When an overcurrent flows through this fuse, the fuse is fused (melts and breaks). Accordingly, the flow of the overcurrent through the protection target is suppressed.
When a fuse as described above is used in a circuit in which a current with a relatively low voltage flows, an overcurrent protection function is realized by the fuse being fused.
However, there is a case where both a current with a relatively low voltage and a current with a relatively high voltage flow depending on a configuration of a circuit in which the fuse is arranged. In such a circuit, if an overcurrent with a relatively high voltage flows through the fuse, there is the concern that arcing occurs and an overcurrent flows continuously even after the fuse was fused.
In order to prevent the arcing, use of a high voltage fuse including a fuse element that is covered with arc-extinguishing sand has been considered. However, high voltage fuses are relatively expensive, and thus there is the problem that the manufacturing cost of an overcurrent protection apparatus increases.
The present application was drafted in view of the above-described circumstances, and it is an object to provide an overcurrent protection apparatus whose manufacturing cost is reduced.
The present application relates to an overcurrent protection apparatus that may be connectable to an external circuit to protect the external circuit from an overcurrent, the overcurrent protection apparatus including a fuse member including a fuse and a fusible wire that may be connected in series to the fuse, the fusible wire being made of a conductor that has a melting point lower than that of copper, and having a fusing current value that may be higher than that of the fuse. The fuse member may be connected in series to the external circuit.
According to the present application, when an overcurrent with a relatively low voltage flows, a fuse having a relatively small fusing current value is fused (i.e. blows). Accordingly, the overcurrent is kept from flowing through the external circuit.
On the other hand, when an overcurrent with a relatively high voltage flows, the fuse and the fusible wire are fused. Since arcing occurs even when the fuse is fused, the current will continue to flow through the fuse. Furthermore, even when the fusible wire has been fused, arcing may occur between terminals of the fused fusible wire. However, by the terminals of the fusible wire being melted due to the heat of arcing, the distance between the terminals of the fusible wire increases. Accordingly, arcing disappears and the current is interrupted. In this way, use of the fusible wire eliminates the need to use a high voltage fuse even when an overcurrent with a relatively high voltage flows. As a result, it is possible to reduce the manufacturing cost of the overcurrent protection apparatus.
The following aspects may be included as embodiments of the present application.
At least the fusible wire may be accommodated in a case.
According to the above-described aspect, it is possible to protect members arranged in the vicinity of the overcurrent protection apparatus from arcing that occurs when the fusible wire is fused and from flying pieces of the fused fusible wire.
A wire-side connector may be arranged at an end of an external electric wire that is connected to the external circuit, and an apparatus-side connector that is electrically connected to the fuse member and into which the wire-side connector may be capable of being fitted be provided in the case.
According to the above-described aspect, it is possible to easily electrically connect the external circuit to the overcurrent protection apparatus by fitting the wire-side connector and the apparatus-side connector together.
The fuse may be a fuse for use in a vehicle.
According to the above-described aspect, a fuse for use in a vehicle that is relatively inexpensive can be used, leading to a reduction in manufacturing cost of the overcurrent protection apparatus.
The fuse may be mounted on a printed board.
According to the above-described aspect, it is possible to downsize the overcurrent protection apparatus.
Moreover, the present application relates to an overcurrent protection apparatus that may be installed in a vehicle, the vehicle being provided with a low voltage circuit through which a current with a relatively low voltage flows and a high voltage circuit through which a current with a relatively high voltage flows, the overcurrent protection apparatus being connectable to the low voltage circuit to protect the low voltage circuit from an overcurrent. The overcurrent protection apparatus may further include a fuse member provided with a fuse and a fusible wire that may be connected in series to the fuse, the fusible wire being made of a conductor that has a melting point lower than that of copper, and having a fusing current value that is higher than that of the fuse, wherein the fuse member may be connected in series to the low voltage circuit.
According to the present invention, the overcurrent protection apparatus may be effective when it is installed in a vehicle provided with a low voltage circuit and a high voltage circuit.
Furthermore, a configuration is also possible in which the high voltage circuit includes a battery module in which a plurality of electric cells are connected in series, and the low voltage circuit includes detection electric wires that detect states of the electric cells.
According to the above-described aspect, the overcurrent protection apparatus having a reduced manufacturing cost may be applied to the battery module.
According to the present application, it is possible to reduce the manufacturing cost of an overcurrent protection apparatus.